This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-119545, filed Apr. 22, 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electronic device, and more particularly to a cooling mechanism that dissipates heat generated from electronic components and cools the electronic device.
2. Description of the Related Art
In recent years, CPUs mounted on electronic devices are getting more improved operating clock frequencies, more increased speeds and performance, and accordingly more increased heat radiation. It is necessary to cool the CPU for maintaining its performance. As a cooling method, a cooling member such as a heat sink is attached to the CPU""s top surface to dissipate heat from the CPU.
Conventionally, an electronic device such as a computer includes a circuit board in its case. The CPU is mounted on this board. There is also available a BGA-type (BGA: ball grid array) CPU whose bottom surface has a plurality of solder balls arranged in matrix form. The CPU""s solder balls are soldered to the circuit board, for example. The heat sink is mounted above the CPU, e.g., via a highly thermal conductive heat transfer sheet for radiating heat from the CPU. The heat sink is made of a highly thermal conductive material such as aluminum that integrally forms a supporting section for fixing the heat sink to the circuit board. The supporting section of the heat sink is screwed to the circuit board so that the CPU is mounted between the circuit board and the heat sink.
In the conventional cooling module, the heat sink is screwed to the case, the circuit board, or the like. The cooling module is structured so that a force applied to screws is directly applied to the CPU. The CPU is heavily weighted in order to ensure a secure connection between the CPU and the heat sink despite various dimensional errors including a CPU""s dimensional error, mounting height variations due to dimensional errors of CPU electrodes such as solder bumps, solder balls, etc., a heat sink""s manufacturing tolerance, and the like.
Recently, it begins to employ a floating structure that mounts the cooling module such as the heat sink on the circuit board via an elastic member. According to this method, the cooling module is appropriately connected to the top surface of the CPU in accordance with mounting height variations of the CPU. Lately, there is available a type of CPU whose element (die) is exposed to the top surface of the package. Such CPU can connect with the floating-structure cooling module. If the CPU has mounting height variations, the elastic member absorbs a height dimension to maintain thermal connection between the element and the cooling module.
Since a notebook personal computer is used in many ways, however, it is subject to vibration and shock during transportation and may be subject to an unexpected external force. If an external force is too large for the floating structure to absorb, it is impossible to ensure thermal surface connection between the die and the heating section. In such a case, the heating section touches part of the die surface to cause a stress to be concentrated, breaking the die surface. The die is easily damaged when the heating section touches corners or sides on the die surface.
As mentioned above, the conventional cooling module has a drawback that a mounting error or usage state may eliminate the surface contact between the heating section and the electronic component and that a stress concentrates on part of the electronic component to damage it.
According to an embodiment of the present invention, an electronic device comprises a case, a circuit board contained in the case, an electronic component which is mounted on the circuit board and comprises a base and a rectangular parallelepiped element mounted on the base, and a cooling module which is thermally connected to the rectangular parallelepiped element and has a heating portion receiving heat from the electronic component, the heating portion being thermally connected to portions other than corners of the rectangular parallelepiped element.